5 rubber stamps cost $5.60. Which equation would help determine the cost of 12 rubber stamps?
Answer: There are several equations that could help determine the cost, each with a slightly different approach. We can write the fact that 5 rubber stamps cost $5.60 as a proportion: $\dfrac{5}{\$5.60}$ Let $x$ represent the unknown cost of 12 rubber stamps. Since 12 rubber stamps cost $x$ , we have the following proportion: $\dfrac{12}{x}$ The cost changes along with the number of rubber stamps purchased, and so the two proportions are equivalent. $\dfrac{5}{\$5.60} = \dfrac{12}{x}$